The present invention relates to an improved apparatus for recombining the molecular oxygen and the molecular hydrogen which are contained in the radioactive waste gas stream found in conventional nuclear power plants.
In the operation of conventional nuclear power reactors, non-radioactive molecular hydrogen and molecular oxygen are produced from steam on the extremely hot surfaces of the fuel elements in the reactor by radiolysis. The operation of conventional nuclear power plants also generates radioactive gases which find their way into the plant steam system and are carried over into the turbines, preheaters and condensers. Among the radioactive gases which find their way into the steam system are nitrogen, oxygen, krypton, xenon, and halogens such as fluorine and iodine. These radioactive gases cannot be released in their original form or concentration and must be passed through various waste treating systems to reduce the levels of the radioactive gases to below acceptable limits.
The mixed gaseous radioactive waste products and the non-radioactive molecular hydrogen and molecular oxygen are removed from the steam turbine condenser along with air that has leaked into the condenser system by a multi-stage steam jet air ejector system which is applied to the condenser. This mixed off-gas stream is then treated to reduce the radioactive gases to the levels permitted by regulation and to recombine the hydrogen and oxygen to water. First, the molecular oxygen and molecular hydrogen are recombined to water in a catalytic recombiner and the water produced therefrom is removed in a condenser. Then, the remaining gases are detained on their path to the exhaust stack in order to allow for decay of radioactivity. Entrained aerosols and solids are generally removed by mechanical separation and filtration.